I should also add to what I listed above: the entire throw happens from the back of uke - not from the front. This also helps prevent the counter.

On the counter coming from the ground (after the throw): it's a bit difficult to counter when the back of your head is caved in; and if the technique was to continue tactically, stomping the front of someone's head to match the back of their head (being caved in) is going to be a lot easier for nage to do than it is for uke to reach up and flick at nage's groin from his/her semi-conscious state.